Trying to decide this bunch for my main theater. My goal is to keep things under $600, and obviously if I can find a great sub for less with close to the same quailty as a $600 sub I'd certainly look at it. Wondering which you think will provide, the deepest, and hopefully cleanest bass. I realize those two might not go together. I should also mention I do not want a 10" subwoofer, because I want the special sound I get with 12" Drivers. Also, if you feel there is another subwoofer I should throw into the list that would be great, it appears this $600 or lower market is a very LONG list, but hopefully I can find the gem.

Wondering which you think will provide, the deepest, and hopefully cleanest bass.

I have no doubt that the SVS will provide the deepest and cleanest bass. It will also have more headroom and dynamic freedom than the others, coming closer to replicating the input signal (the goal, btw).

Thanks for comments on the DIY idea. Shane I do agree, I'm leaning towards the svs pb12. In regards to the 12" driver have a special sound, yes it certainly does in most situations. Obviously there are some 10" drivers that can sound as good as a 12" driver although they will cost more because of the extra points they need to compensate for lost surface area and added xmax. The amount of money used in its design to component this. Sure, You can spend 1,000 on a 10" sub. But for $600 I can buy a 12" sub that will sound as good if not better. One main aspect of creating bass is the goal of moving air, obviously a 12" has more cone area then a 10" driver.

My point being, that I want a 12" because of its value, and I really don't care what any tests on paper say..

a 10" does not have the same musical tone as a 12" driver, just like a 15" driver doesn't sound like a 12" driver. If a 10" subwoofer sounded like a 12" or 15" driver I have no idea why anyone would not want that, I mean they are smaller and more compact. Why in the world do people buy 12" or 15" woofers, heck lets all buy 8" woofers.

Interesting comments, Stonepran. I certainly disagree with almost everything you posted, based on my DIY experience, but there's much more that goes into a good post than just facts.
What makes the "musical tone"of a 12" driver better than a 10", or different from a 15"? Leaving out output, or just your impressions, try to provide some facts or evidence.
Always trying to learn...thanks.